1. Field of the Invention
The present invention relates generally to a plate type heat exchanger for two different fluids, and more particularly to a so-called housing-less automotive heat exchanger usable in combination with an oil filer.
2. Description of the Prior Art
In connection with automotive plate type heat exchanger used for cooling engine lubricating oil, a so-called housing-less heat exchanger has been already proposed in which a plurality of heat exchange units are piled up and secured to each other in such a manner that a lubricating oil flowing space and a cooling water flowing space are alternately formed, thus forming a heat exchange element. Each heat exchange unit is constructed of upper and lower heat transmission plates of different shapes, so that the lubricating oil flowing space and the cooling water flowing space are defined on the opposite sides of each of upper and lower heat transmission plates. Accordingly, heat exchange between the lubricating oil and the cooling water is accomplished through each of the upper and lower heat heat transmission plates.
However, difficulties have been encounted in such a conventional housing-less heat exchanger because each heat exchange unit is constructed of two kinds of heat transmission plates of the difference shapes. That is to say, two kinds of heat transmission plates are unavoidably required to form the heat exchange element and therefore the productivity of the heat exchanger is lower while increasing the production cost thereof. Additionally, the two heat transmission plates of the different shapes are relatively difficult to tightly and sealingly fit each other, thus causing possibility of leaking of the lubricating oil and/or the cooling water.